Molded objects respectively composed of a resin reinforced by groups of reinforcing fibers consisting of numerous continuous filaments (FRPs) are widely used as various parts and members of structural bodies. Molded objects respectively using a thermosetting resin as a matrix are produced by such molding methods as press molding of a prepreg impregnated with a thermosetting resin and resin transfer molding (RTM).
However, an FRP composed of a thermosetting resin is not suitable for producing a complicatedly shaped part or structural body by a single molding process. As a consequence, a part or structural body having a complicated shape is produced by producing plural members from the FRP and integrating those members.
The integration methods include mechanical bonding methods using bolts, rivets, screws and the like and bonding methods using adhesives. A mechanical bonding method has such problems that the reduction of production cost is very difficult since a step for machining bonding portions beforehand is necessary and that application is limited in view of appearance. A bonding method using an adhesive has such problems that the reduction of production cost is very difficult since a bonding step including the pre-arrangement of an adhesive and adhesive application work is necessary, and that no sufficiently satisfactory reliability can be obtained in the bonding strength.
A method for integrating a member formed of a thermoplastic resin and a member formed of an FRP composed of a thermosetting resin is proposed in JP10-138354A. This method comprises a first step of laminating a thermoplastic resin film on the surface of a prepreg consisting of reinforcing carbon fibers and a thermosetting resin, for forming a first layered product, a second step of applying a heat and pressure to the obtained first layered product under such conditions as setting the thermosetting resin but not causing the film to flow, to form a second layered product composed of a carbon fiber reinforced thermosetting resin having the thermoplastic resin film sticking to it, and a third step of injection-molding a thermoplastic resin onto the surface of the thermoplastic resin film of the second layered product placed in a mold, to bond the thermoplastic resin member (core member) formed by the injection molding and the second layered product (surface member) to each other. According to this method, since the core member composed of a thermoplastic resin and the surface member are joined through the thermoplastic resin film of the surface member, there is no special problem in the bonding strength at the joint.
However, there is a problem that the bonding strength at the joint between the thermosetting resin and the thermoplastic resin film in the surface member is not sufficient. The reason is that the latter joint is formed by bonding between a thermosetting resin and a thermoplastic resin, namely, bonding between different materials.
An object of the invention is to provide a layered product that reduces the conventional fear about the bonding strength in the bonding between different materials.
Fiber reinforced resins (FRPs) are widely used as materials for forming various products. On the other hand, the weight reduction of these products is being demanded. Above all, as portable electronic apparatuses typified by notebook personal computers, cellular phones and portable information terminals are increasingly popularly used, thinner and lighter-weight products are strongly demanded in the market. In this connection, it is demanded that the housings and internal members constituting the products are reduced in thickness and weight and enhanced in stiffness.
To meet this demand, magnesium alloys are used anyway. The demand for higher stiffness further grows, and the use of metallic materials with higher stiffness such as aluminum alloys is being studied. However, it is difficult to easily produce complicatedly shaped parts and products at high productivity from these metallic materials.
JP 2001-298277 A proposes a housing obtained by integrally bonding a metallic molded object and injection molded ribs using an epoxy resin-based coating material. JP06-029684A proposes an electromagnetic-shielding housing obtained by integrating a metallic sheet and a molded synthetic resin object. However, these housings cannot satisfy the demand for lighter weight, since the specific gravity of the metallic material is large, though they can satisfy the demand for smaller thickness and higher stiffness.
Considering the recycling of products, it is difficult to separate and sort the products obtained by integrating members formed of different materials into the respective members. As a result, contaminants consisting of different materials are generated to pose such problems that it is difficult to reuse those members and that the cost of recycling increases.
In view of the problems of the prior art, an object of the invention is to provide a layered product that can be easily integrated with another structural member at excellent bonding strength, and also to provide a process for producing it. The integrated molded object obtained by using the layered product is excellent not only in mechanical properties, light weight and electromagnetic shielding performance but also in design flexibility and recyclability, and can be used suitably as a housing of an electric or electronic apparatus or portable information terminal, or as a structural member of a transport apparatus such as a motor vehicle or aircraft.